Steam-boiler.



no. 7l5,842. v Patented Dec. l6, I902.

B. McKAY.

STEAM BOILER.

(Application fiIedJuno B. 1902.) (No Modal.)

4 Sheots-Shaet 2.

-Witnesss Q/gQ/{Qy lriventor,

Attorneys N0. 7l5,842. Patonted D6 0. I6, I902.

B. MGKAY.

STEAM BOILER.

(Appliution fllQd Juno 2, 1909.) (lfl'lflllam 4 Shack-Sheet 3.

JL M ifv Witnesses: fl g jg- K y Inventor,

Q .7 WW

62 3/ Attorneys m: "hams PETERS 00v. Pnumumq. wuumzmm. D4 c.

Patented Dec. I6, I902. B. McKAY. STEAM BOILER. Application filed tuna2, 1902.)

QSheets-Sheai 4.

F I a. l].

Inventof,

Attorneys l ll I .l

No. 7l5,842.

(No Model.)

wltnesses: F$

UNrrnn STATES PATENT OFFICE.

ROBERT MOKAY, OF QUEBEC, CANADA.

STEAM- BOILER.

$PECIFIGATION forming part of Letters Patent No. 715,842, dated December16, 1902.

Application filed June 2; 1902.

To aZZ whom it fitay concern;

Be it known that I, ROBERT MCKAY, a subject of the King of GreatBritain, residing at the city of Quebec, Province of Quebec, Canada,have invented certain new and useful Improvements in Steam-Boilers; andI do hereby'declare that the following is a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to whichitappertains to make and use the same.

My invention relates to a steam-boiler of what is known as the verticaltype, being of a generally cylindrical pattern, with a firechamber inthe lower end, and arranged to have the gases of combustion pass throughfire-tubes to a combustionchamber in the upper end.

The object of my invention is to produce a boiler of very largelyincreased steaming capacity over those now in common use-that is to say,one which shall evaporate a much greater quantity of water in a giventime than any boiler of the same size now in use and yet at the sametime which shall so fully utilize the heat of the gases of combustion asto allow a minimum of heat to escape into the air, thus adding to itsmerits that of a maximum of efficiency.

Another object of my invention is to produce a boiler which, whilehaving a very greatly increased heating-surface, yet may be readilytaken apart and cleaned, permitting of access to all parts of theboiler, which shall be constructible ata minimum of cost and becomparativelyfree from the necessity of frequent and extensive repairs,and which shall be to a certain extent self-cleaning and not liable toget out of order from differences in the expansion and contraction ofthe individual parts and other like causes, which are a frequent sourceof both expense and disaster with most types of boilers. g

The usual type of vertical boiler is' constructed with a cylindricalshell, capped at top and bottom by a pair of circular heads, betweenwhich pass a series of vertical tubes, and up these tubes the gases ofcombustion are adapted to pass on their way to the chimney. The water iscontained within the shell, and owing to the fact that this water cannotentirely cover the tubes-that is to say, must stand at a certain levelwithin the shell, so

as to leave the upper ends of the tubes unprotected-the latter are aptto become highly heated at their upper ends, which are not surrounded bywater, and this causes frequent leaks and the escape of steam andpressure in a manner that is often wholly unaccountable by reason of thefact that these upper ends of the tubes are concealed within thesmoke-box, so that the leak or leaks cannot be observed while the boileris in operation. Moreover, this causes a corrosion of the tubes at theupper ends, so that they have to be taken out and replaced by others,and the expansion of the tubebeing greater than that of the boiler-shelltends to bulge and warp thehead unevenly, and thus increase the tendencyto leak. It is my special object in'the present invention to avoid andovercome these defects by providing firetubes which'shall be completelycovered with water and another set of fire-tubes through which thecombustion-gases are adapted to pass subsequently to the passage of thefirst set and after they have been cooled down to a comparatively lowtemperature, and these last-named tubes are arranged to be free fromwater throughout nearly their entirelength.

Another defect of the present type of vertical boiler in use is that thecombustion or socalled smoke-chamber, which is provided for the gasesabove the tubes, is located entirely above the water and steam to beheated, so that the eifect of these hot gases and the combustion thereofis practically lost, except so far as it is communicated by downwardradiation to the upper tube-sheet of the boiler. It is therefore anotherimportant object of this invention to-remedy this defeet by providing aprimary or intermediate combustion-chamber located in the midst of theboiler and surrounded on both sides by water, whereby during the fulland complete combustion of the gases the heat thereof may becommunicated not simply by radiation to the tube-sheet below the saidsmoke-chamber, but likewise by both radiation and convection also to thelower tube-sheet of the upper boiler-section on the upper side of thesaid smoke-chamber.

Another object of my invention is to combine the merits of theWater-tube and firetube types of steam-boiler by providing concentricwater and fire tubes, the former arranged to be inclosed by and dependwithin and concentric with the latter, whereby the gases of combustionare caused to pass up in annular form between two bodies of water, thusas completely as possible extracting from them their contained heat.

To these and other ends, which will hereinafterappear,myinventionconsists,substan tially, of a compound tubular shell, ordinarilycylindrical in outline, composed of three sections mounted end to end.The lower section of the shell is provided, preferably, with afire-chamber in its lower end, having an interior concentric shellforming a water-leg for that purpose, and the two ends of the shell thusformed are capped by two circular heads, between which pass a number ofvertical tubes in the same manner as in the ordinary vertical boiler, sothat this lower section forms substantially a boiler in itself.Immediately above this and separated from it by an intermediate space isplaced the third section, which is in the shape of a plain cylindricaldrum capped by two heads, between which pass another series offire-tubes; but the third section is operatively connected with thefirst section by a series of short connecting-pipes, so that the lowersection is arranged to be completely filled with water, and the level ofthe water will stand close to the lower head of the upper or thirdsection just mentioned, thus substantially separating the water-holdingand the steam-holding parts into two separate chambers. Between thesetwo sections is located the second section of the boiler, which is alsoa plain cylindrical drum, but without heads, and the three are thusjoined end to end, the second section inclosing asmoke or combustionspace between the first and third sections, and thus increasing notsimply the heating area, but also the facility of combustion, whileabove the third section is attached an additional or secondarysmoke-chamber, which leads to the chimney.

My invention further consists in providing a series of water-tubesdepending from the lower side of the upper section of the boiler, whichwater-tubes are arranged to depend right through the primarysmoke-chamber above mentioned and into and through the fire-tubes of thefirst section, so as to form water-tubes within the fire-tubes, and thuscombine the merits of both types of apparatus in a manner which, so faras known to me, is entirely novel.

My invention further consists in the construction and combination ofparts, which will appear from the following description and are moreparticularly pointed out in the claims.

In the drawings accompanying this specification I have shown thepreferred form of my improved steam-boiler, and herein Figure 1 is aside elevation of the boiler. Fig. 2 is a vertical central sectionthereof.

Fig. 3 is a horizontal or plan section taken on the line 3 3 of Fig.2-that is to say, just above the upper tube-sheet of the steam-section.Fig. 4 is a similar horizontal or plan section taken on the line 4 4 ofFig. 2-that is to say, just above the lower tube-sheet of the samesection. Fig. 5 isasimilarhorizontal or plan section taken on the line 55 of Fig. 2-that is to say, just above the upper tubesheet of the loweror water section. Fig. 6 is a similar horizontal or plan section takenon the line 6 6 of Fig. 2that is to say, just above the crown-sheet ofthe boiler. Fig. 7 is a vertical central section of the lower or Watersection of the boiler as separated from the remainder of the boilerduring the process of cleaning, inspecting, or repairing the same. Fig.8 is a vertical central section of the second or smoke-box section whichconnects the water and steam sections. Fig. 9 is a vertical centralsection taken through the upper or steam section as separated from theother section in the process of cleaning, inspecting, or repairing thesame. Fig. 10 is a perspective view of the interior of the boiler withthe front portion of the shell removed. Fig. 11 is an enlargedfragmentary view showing the junction of the first, second, and thirdsections of the boiler. Fig. 12 is also an enlarged fragmentary detailview of the hollow stay-bolts or water-pipes connecting the water andsteam sections.

The same numerals of reference denote like parts in all the figures ofthe drawings.

The three sections of the boiler, as shown in the drawings, aredesignated, respectively, as 11, 12, and 13, the lower being thewatersection, the middle one the smoke-box or connecting section, andthe upper the steam-section. The two sections 11 and 13 are each formedof a cylindrical shell or boiler-plate 14 and 15 of the same diameter.Interiorly of the lower'seetion 11 and at the lower end thereof there isformed a fire-chamber 16 by means of a concentric shell 17, attached tothe shell 11 at its lower end by rivets 18, but separated therefrom by ahoop 1.), thus forming a water-leg 20, surrounding the chamber 16, andthis fire-chamber is provided with a suitable grate 21 and an opening 22in the front side, provided with a hinged fire-door 23, mounted on apintle 24 and provided with a latch 25. The upper side of thefire-chamber 16 is closed by the crown-sheet 26, which is bored with anumber of holes for the reception of the lower ends of a series offire-tubes 27, which are expanded or otherwise secured therein and whoseupper ends are likewise expanded or otherwise secured in suitableapertures in the upper tube-sheet 28, which is attached to the upper endof the shell 14 by rivets 29, whose exterior heads are countersunk flushwith the surface of the shell 14. As shown in Figs. 5 and 6, the boilerherein illustrated is provided with sixty-one of these tubes, arrangedin the form of a regular hexagon.

The upper or steam section of the boiler 13 is formed, as aforesaid, ofthe cylindrical shell 15, which is in general considerably shorter thanthe shell 14 of the section 11 and is inclosed at its two ends by lowerand upper tube-sheets and 31, which are connected by a series ofvertical fire-tubes 32 in the same manner as the heads of the lowersection and as shown in Figs. 3 and 4, there being provided herein, asshown, thirty of these tubes, twelve of which are located directly overthe ends and coaxial with corresponding tubes 27 of the lower section;but the remaining ones are located around the margin of the sheet, so asto give room for the insertion of the water-tubes 33 in the lower sheetof the steam-section, as will be presently described, and, further, tocheck the passage of the gases in the space between the upper and lowerboiler sections and cause the gases to pass horizontally in order tofind exit, thus further commingling and becoming fully burned, as wellas more thoroughly communicating the heat by radiation and convection tothe adjacent heating-surface.

The upper and lower sections 13 and 11 are furthermore connected by aseries of hollow stay-bolts or water-pipes 34, which are threaded atboth ends, as shown, and are in the boiler herein illustrated seven innumber that is to say, one at the center and six around the margins ofthe sheets 28 and 30. These tubular bolts 34 are threaded at their lowerends into the heads 28, as shown, or may be otherwise permanently fixedthereto and expanded therein, if necessary; but the upper ends of thebolts 34 are removably connected with the head 30 of the upper sectionby means of a pair of hexagonal nuts 35 and 36, mounted, respectively,below and above the sheet 30, so as to clamp the same tightly betweenthem, and to increase and solidify the strength and tightness of thejoint I may insert asbestos washers 37. The nature of this joint is moreclearly illustrated, on an enlarged scale, in Fig. 12.

In connecting the upperand lower sections 13 and 11 to each other thebolts 34 are first screwed into the head 28 of the lower section, asshown in Fig. 7, after which the lower nuts 35 are ,properly placed uponthe upper ends of the bolts. After this the lower head 30 is placed uponthe ends of the bolts 34 and the upper nuts 36 screwed thereover, theproper asbestos washers having been of course inserted in the joint. Toenable the nuts 36 to be adjusted and tightened, as well as removedduring the operation of taking apart the boiler, I provide the upperhead 31 with a series of seven apertures 37, each closed by a screw-plug38, having a polygonal head 39, these plugs being located immediatelyover the respective tubes 34, so that by removing the plugs asocket-wrench may be inserted into each of the holes and the nuts 36tightened in place, after which the plugs 38 are for the passage of thegases.

screwed in to close the apertures 37 and render the section 13steam-tight.

As hereinbefore observed, the twelve cen' trally-located fire-tubes 32of the steam-section are directly over the corresponding firetnbes 27 ofthe lower section, and the passage-ways through the lower tubes are thusopen for their entire length and free from obstructions; but theremaining fire-tubes 27 of the lower section have each dependingtherethrough and concentrically therewith a water-tube 33, which issufficiently small to pass through the corresponding tube 27, leaving anannular space between the two tubes The tubes 33 are properly expandedor otherwise fixed into suitable apertures in the tube-sheet 30, being,as herein shown, forty-eight in number, and they depend a certaindistance below the crown-sheet 26, as shown in Fig. 2, their lower endsbeing closed. These tubes very greatly add to the efficiency andcapacity of the boiler by assisting in the extraction of heat from thegases and spreading out the latter in their passage through thefire-tube into a thin annular sheet.

The water and steam sections 11 and 13 are solidly connected together bythe bolts 34 in the manner above described; but in order to inclose thespace between the two heads 28 and 30 thereof and form acombustionchamber I provide the intermediate inclosing section 12, whichis in the nature of a simple cylindrical band or belt surrounding theinclosed space. As herein shown, this belt is formed of two annularsheets 40 and 41, the inner one of which, 40, is of the same diameter asthe cylindrical shells 14 and 15 and forms a continuation thereof, beingjointed thereto by the oblique joints 42 and fitting closely over theflanges 43 and 44 of the sheets 28 and 30, where they are joined totheir respective shells by rivets 29 and 45, both countersunk on theirouter sides, so as to be flush with the surfaces of the shells 14 and15. The outer piece 41 of the section 12 is sufficiently long, as shown,to overlap a portion of the ends of the shells 14 and 15, so that thelatter will be solidly driven thereinto and engaged therewith when theboiler is set up and before screwing up the nuts 36. The two sheets 40and 41 are connected together by a series of rivets 46. This arrangementforms a substantially tight joint and prevents the escape of thecombustion-gases around the edges of the joint, while at the same timepermitting the sections of the boiler to be readily separated. Thecombustion-chamber, inclosed by the section 12 and the heads 23 and 30,is designated by the numeral 47. To the upper end of the upper section13 I may connect a suitable conicalshell 48 by means of the rivets 49,which join the tube-sheet 31 to the shell 15, thus forming a secondarysmoke-box 50, at the upper end of which is connected a stack 51.

I have herein shown the usual appendages of a steam-boiler, consistingof a water-gage 52, attached to the steam-section, and an inlet andblow-0E pipe 53 and 54, connected at the back of the water-section, asusual; but of course these do not form a part of my invention. Thewater-line, as illustrated in Figs. 1 and 9, is arranged to standordinarily near the bottom of the upper or steam section 13, so that thelatter is filled almost completely with steam, while the lower section11 is completely filled between the two heads thereof with water, andthe steam that is generated therein passes up through the tubular bolts34, which permit the circulation of the water. The depending watertubes33 provide for an additional circulation of water independently of thewatersection 11. The arrangement thus provided causes the lower seriesof fire-tubes 27 to be uniformly heated throughout their length and toextract the greater part of the heat of the combustion-gases before theypass into the combustion-chamber 47. \Vhile in this chamber thecombustion is completed and the heat thereof radiated and conducted byconvection to the water located on both the upper and lower sides ofthis chamber, after which the gases thus materially cooled pass throughthe upper fire-tubes 3:2, and thus while the last of the heat is enabledto be extracted from the gases at the same time there is no danger ofoverheating of the tubes. The upper tubes 32 are surrounded for theirentire length, wit-h the exception of a small portion atthe lower endsthereof, by steam, so that they are uniformly heated, and the steamcontained in the upper section is not only kept free from Water, but isenabled to be superheated, so as to evaporate any possible water whichmight be held in suspension therein. I have found by experience that theclosed water-tubes 33 do not get overheated nor clogged with dirt,because the high heat to which they are subjected causes the water to becontinually circulated through them, passing down through the center andup around the sides, and this circulation is so rapid as to prevent anydirt settling at the lower ends and keeping them clean and brightinteriorly. \Vhen the boiler is taken apart, these tubes may be readilyreplaced when worn out. The lower section of the boiler may be cleanedthrough one or more suitable handholes 55, as usual.

While I have shown in the accompanying drawings the preferred form of myinvention and have illustrated it as applied to boilers of the verticaltype, it will be understood that, broadly speaking, the main features ofthe invention, especially that feature which relates to the water-tubelocated within the fire-tube, may be applied to any type of boileras,for instance, those having horizontal or oblique tubes-and other changesmay be made which will not interfere with the principle of'my invention,and I therefore do not limit myself to the precise form shown nor to thedetails as described, for these may be changed in form or positionwithout affecting the operativeness or the utility of my invention, andI therefore reserve the right to make all such modifications and'such aslie within the scope of the following claims or of mechanicalequivalents to the structures set forth therein.

Having thus described my invention, what I claim as new, and desire tosecure by Letters Patent, is-

1. A boiler comprising a cylindrical watersection having parallelfire-tubes connecting the heads thereof, a cylindrical steam-sectionlocated above said water-section, a series of fire-tubes coaxial withsaid first-named tubes and connecting the heads of said steam-sectionand a series of connections between said sections whereby the tubes ofsaid water-sections are completely surrounded by waterand the level ofthe water stands at a point within the said upper section.

2. A steam boiler comprising a vertical lower or water section adaptedto be completely filled with water, a series of fire-tubes joining theheads thereof, a steam-section above said water-section, a series offire-tubes coaxial with said first-named tubes joining the heads of saidsteam-section, and a series of water connections joining the adjacentheads of the water and steam sections.

3. A steam-boiler comprising a closed cylindrical vertical drum havingupper and lower heads, a series of separate cylindrical water-tubesdepending from secured to and supported by the lower head of said drumand having closed lower ends, and a series of fire-tubes connecting thetwo heads of said drum.

4. A steam-boiler comprising a lower upright water-drum havinghorizontal upper and lower heads, a series of fire-tubes connecting saidheads, a second drum of equal diameter located above said lower drum, anindependent series of fire-tubes connecting the heads of said upperdrum, and a series of water-tubes depending from the lower head of saidupper drum and passing through the fire-tubes of said lower-drum.

5. A steam-boiler comprising a lower upright water-drum havinghorizontal upper and lower heads, a series of fire-tubes connecting saidheads, a second drum of equal diameter located above said lower drum, anindependent series of fire-tubes connecting the heads of said upperdrum, a series of water-tubes depending from the lower head of saidupper drum and passing through the fire-tubes of said lower drum, andan'inclosing wall connecting the lower head of the upper drum with theupper head of the lower drum, whereby to form a combustion-chamberbetween them.

6. A steam-boiler comprising a vertical Water-drum having horizontalupper and lower heads, a series of fire-tubes connecting said heads, anupper vertical steam-drum above said water-drum andof equal diametertherewith and having also horizontal upper and lower heads, a series offire-tubes connecting the heads of said steam-drum, and a series oftubular bolts at different radial distances from the center connectingthe upper head of the lower drum with the lower head of the upper drumwhereby to maintain the circulation of water between the two drums.

7. A steam-boiler comprising a vertical water-drum having horizontalupper and lower heads, a series of fire-tubes connecting said heads, anupper vertical steam-drum above said water-drum and of equal diametertherewith and having also horizontal upper and lower heads, a series offire-tubes connecting the heads of said steam-drum, a series of tubularbolts connecting the upper head of the lower drum with the lower head ofthe upper drum whereby to maintain the circulation of water between thetwo drums, and a series of Water-tubes having closed lower endsdepending from the lower head of the upper drum through and concentricwith the fire-tubes of the lower drum.

8. A steam-boiler comprising a vertical water-drum having horizontalupper and lower heads, a series of fire-tubes connecting said heads, anupper Vertical steam-drum above said water-drum and of equal diametertherewith and having also horizontal upper and lower heads, a series offire-tubes connecting the heads of said steam-drum, a series of tubularbolts connecting the upper head of the lower drum with the lower head ofthe upper drum whereby to maintain the circulation of water between thetwo drums, a series of water-tubes having closed lower endsdepending'from the lower head of the upper drum through and concentricwith the fire-tubes of the lower drum, and an inclosing wall connectingthe walls of the two drums, whereby to form an i'nclosedcombustion-chamber between the two drums, substantially as described.

9. A steam-boiler comprising an upright cylindrical lower drum having afire-chamber formed at the lower end thereof, a crown-sheet closing thelower end of said drum above said fire-chamber, an upper tube-sheetclosing the upper end of said drum, a series of fire-tubes connectingsaid crown and upper tube sheets, a cylindrical steam-drum of equaldiameter to said water-drum and located above the same, said drum havingalso parallel upper and lower tube-sheets inclosing it, an independentseries of fire-tubes connecting the two sheets of said steam-drum, and acylindrical intermediate belt inclosing the space between the two drums,whereby to form a combustion-chamber.

10. A steam-boiler comprising an upright cylindrical lower drum having afire-chamber formed at the lower end thereof, a crown-sheet closing thelower end of said drum above said fire-chamber, an upper tube-sheetclosing the upper end of said drum, a series of fire-tubes connectingsaid crown and upper tube sheets, a cylindrical steam-drum of equaldiameter to said water-drum and located above the same, said drum havingalso parallel upper and lower tube-sheets inclosing it, an independentseries of fire-tubes connecting the two sheets of said steam-drum, acylindrical intermediate belt inclosing the space between the two drums,whereby to form a combustion-chamber, and a series of tubular boltsremovably connecting the adjacent heads of the two drums and permittingthe circulation of water therethrough.

11. A steam-boiler comprising an upright cylindrical lower drum having afire-chamber formed at the lower end thereof, a crown-sheet closing thelower end of said drum above said fire-chamber, an upper tube-sheetclosing the upper end of said drum, a series of firetubes connectingsaid crown and upper tube sheets, a cylindrical steam-drum of equaldiameter to said water-drum and located above the same, said drum havingalso parallel upper and lower tube-sheets inclosing it, an independentseries of fire-tubes connecting the two sheets of said steam-drum, acylindrical intermediate belt inclosing the space between the two drums,whereby to form a combustionchamber, a series of tubular boltsremovably connecting the adjacent heads of the two drums and permittingthe circulation of water therethrough, said upper sheet of said upperdrum having a series of orifices therein immediately over the ends ofsaid tubular bolts, and a series of plugs closing said orifices.

12. A steam-boiler comprising an upright cylindrical lower drum having afire-chamber formed at the lower end thereof, a crown-sheet closing thelower end of said drum above said fire-chamber, an upper tube-sheetclosing the upper end of said drum, a series of fire-tubes connectingsaid crown and upper tube sheets, a cylindrical steam-drum of equaldiameter to said water-drum and located above the same, said drum havingalso parallel upper and lower tube-sheets inclosing it, an independentseries of fire-tubes connecting the two sheets of said steam-drum, acylindrical intermediate belt inclosing the space between the two drums,whereby to form a combustionchamber, a series of tubular bolts removablyconnecting the adjacent heads of the two drums and permitting-thecirculation of water therethrough, and a secondary combustion-chamber orsmoke-chamberinclosing the upper end of said upper drum and connect ingit with a stack.

13. In a steam-boiler, the combination of two cylindrical drums of equaldiameter, pipes operatively and removably connecting the two drums andpermitting the passage of water and steam between them, and a removableconnection comprising a pair of annular plates one within the otherarranged to telescope over the cylindrical walls of the two drums,substantially as described.

14:. A steam-boiler comprising a cylindrical water-drum adapted to becompletely filled with water, and having upper and lower horizontaltube-sheets, a fire-chamber formed in the lower end of said drum andvsurrounded by a water-leg, an upright cylindrical steamdrum of equalsize with said water-drum and having upperand lower horizontaltube-sheets inclosing it, said steam-drum being mounted above andcoaxial with said Water-drum and separated therefrom by a shortintervening space, one or more independent tubes or flues connecting thetwo heads of each drum, an annular belt comprised of one or moreconcentric plates adapted to telescope over the adjacent ends of the twodrums to tightly inclose the space between them, a series of shortstraight tubular connecting-bolts connecting the adjacent heads of thetwo drums, and an upper conical smoke-box inclosing the upper end ofsaid upper drum and connected with the stack. a

15. Asteam-boiler com prising a cylindrical water-drum adapted to becompletely filled with water, and having upper and lower horizoutaltube-sheets, a fire-chamber formed in the lower end of said drum andsurrounded by a water-leg, an upright cylindrical steamdrum of equalsize with said water'drum and having upper and lower horizontaltubesheets inclosing it, said steam-drum being mounted above and coaxialwith said waterdrum and separated therefrom by a short interveningspace, one or more independent tubes or flues connecting the two headsof each drum, an annular belt comprised of one or more concentric platesadapted to telescope over the adjacent ends of the two drums to tightlyinclose the space between them, a series of short straight tubularconnectingbolts connecting the adjacent heads of the two drums, an upperconical smoke-boxinclosing the upper end of said upper drum andconnected with the stack, a series of removable nuts mounted on theupper ends of said connecting-bolts, a series of plugs mounted inapertures in the upper sheet of said steam-drum coaxial with saidtubular bolts, whereby to permit the insertion of a socketwrench forturning said nuts, and a series of straight water-tubes connected withand depending from the lower head of said steamdrum through andcoaxially with the fines or tubes of said water-drum and closed at theirlower ends, substantially as described.

In witness whereof I have hereunto set my hand in the presence of twowitnesses.

ROBERT MCKAY. WVitnesses:

J. A. MARION, T. MYNARD.

